Vertebral alignment and fixation assembly

ABSTRACT

A method and apparatus for aligning and fixing vertebral bodies is provided. The vertebral alignment/fixation assembly of the current invention comprises a hemispherical headed pedicle screw disposed within a slotted coupling unit designed to allow angular adjustment of the pedicle screw up to 90° and which may be securely locked into position via a single threaded locking nut once a standard alignment rod has been inserted into the slotted coupling unit. The vertebral alignment/fixation assembly enabling the angular adjustment of the fixation system hardware after final placement and insertion of the pedicle screw into the vertebral body. A system and method for aligning and fixing vertebral bodies using the vertebral alignment/fixation assembly of the invention is also provided.

FIELD OF THE INVENTION

The present invention relates generally to a method and apparatus foralignment and fixation of vertebral bodies.

BACKGROUND OF THE INVENTION

Pedicle screws allow spine surgeons to attach rods or plates to thethoracic and lumbar spine. This rigidly immobilizes the spine segments,promoting the bone graft to grow into a fusion, welding spinal segmentsinto one solid unit, reducing pain and stabilizing deformity withoutrequiring complete immobilization of the patient for the extended periodof time during the healing process.

While many different pedicle screws have been developed, presently mostpedicle screws are fixed axis devices which must be carefully alignedduring insertion and fixation in the spine. Specifically, the screwsmust be drilled or screwed into the bone at a very specific angle toassure that the alignment hardware is exactly positioned such that thereceiving portions of the fixation hardware are aligned so that the rodcan be passed therethrough without distorting the screw or putting anundesirable level of stress on the attachment point. As a result, thealignment procedure requires a considerable amount of time, increasingthe possibilities of complications during surgery and, in many cases thealignment fails and must be repeated. Further, the insertion of thescrew is dependent on the angle of alignment required, resulting ininsertions that are not in the most secure or safe positions withrespect to the vertebral bodies.

The art contains a variety of pedicle screws which permit a level offreedom with respect to the alignment of the screw and the couplingelement. However, these teachings have generally been complex, andinadequately reliable with respect to durability. The considerabledrawbacks associated with the prior art systems include limited angularadjustability, complexity, difficult of properly positioning thecoupling elements and the rod, tedious manipulation of the many partsassociated with the complex devices and the considerable cost associatedwith manufacturing such complex mechanisms.

Accordingly, a need exists for an inexpensive, durable and simplevertebral alignment assembly that allows a surgeon to freely manipulatethe alignment of the coupling hardware such that the fixation rods canbe properly positioned with respect to the vertebral bodies without atime consuming and potentially dangerous alignment procedure.

SUMMARY OF THE INVENTION

The present invention relates generally to a method and apparatus foraligning and fixing vertebral bodies. More specifically, the presentinvention is directed to a vertebral alignment/fixation assembly andmethod which allows a surgeon to manipulate and align the unit couplingthe fixation hardware with the pedicle screw, the assembly comprising ahemispherical headed pedicle screw disposed within a slotted couplingunit designed to allow angular adjustment of the pedicle screw up to 90°and which may be securely locked into position via a single threadedlocking nut once a standard alignment rod has been inserted into theslotted coupling unit. The vertebral alignment/fixation assemblyenabling the angular adjustment of the fixation system hardware afterfinal placement and insertion of the pedicle screw into the vertebralbody.

In one embodiment, the vertebral alignment/fixation assembly of thecurrent invention generally consists of three main components: ahemispherical pedicle screw, a slotted coupling unit designed to receivethe pedicle screw and an alignment rod, and a securing nut for fixingthe angular position of the coupling unit and the position of thealignment rod within the coupling unit.

In one alternative exemplary embodiment, the pedicle screw of theinvention has a slotted tip to allow the screw to self-tap the vertebralbody and thereby ease the insertion of the screw into the bone.

In another exemplary embodiment the portion of the securing nut whichengages the alignment rod is textured to provide a more secure grip ofthe alignment rod.

In still another exemplary embodiment the securing nut has an annularchannel disposed such that a screw driver can be inserted therethroughand interact with the pedicle screw to drive the screw into a vertebralbody.

In yet another exemplary embodiment the pedicle screw is provided with asquare opening in its hemispherical head such that a square headeddriving tool can be mated therewith to drive the screw into thevertebral body.

In still yet another exemplary embodiment the components of the systemare made from an orthopaedically suitable material, such as, forexample, stainless steel or titanium.

In still yet another preferred embodiment, the invention is directed toa system for aligning and fixing vertebral bodies comprising amultiplicity of vertebral alignment components as described aboveattached at suitable points of attachment as determined by the deformityof the spine.

In still yet another embodiment, the invention is directed to a methodfor aligning vertebral bodies. The method comprises manipulating,aligning and fixing the spine using a vertebral alignment system asdescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a side view of an embodiment of an unassembled pedicle screwaccording to the invention.

FIG. 2a is a side view of an embodiment of a partially assembled pediclescrew according to the invention.

FIG. 2b is a front view of an embodiment of a partially assembledpedicle screw according to the invention.

FIG. 2c is a front partial cross-sectional view of an embodiment of apartially assembled pedicle screw according to the invention.

FIG. 3a is a top view of an embodiment of a securing nut according tothe invention.

FIG. 3b is a cross section of an embodiment of a securing nut accordingto the invention.

FIG. 3c is a side view of an embodiment of a securing nut according tothe invention.

FIG. 4a is a side view of the interrelation of an embodiment of apedicle screw and screw driver according to the invention.

FIG. 4b is a cross section of the interrelation of an embodiment of apedicle screw and screw driver according to the invention.

FIG. 5 is a side view of an assembled pedicle screw according to theinvention.

FIG. 6 is a schematic view of the manipulation and alignment of thespine utilizing an embodiment of the vertebral alignment/fixation systemaccording to the invention.

FIG. 7 is a schematic view of the manipulation and alignment of thespine utilizing an embodiment of the vertebral alignment/fixation systemaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates generally to a method and apparatus foraligning and fixing vertebral bodies. More specifically, the presentinvention is directed to a system and method which allows a surgeon tomanipulate the angular alignment of the fixation hardware of a vertebralalignment/fixation system after insertion and fixation of the pediclescrews into the vertebral bodies using freely rotatable couplers mountedto hemispherical pedicle screws. The system and method is furtherdesigned to enable the fixation of the angular alignment andinstallation and fixation of the alignment rods to the couplers byapplication of a single securing nut.

As shown in FIGS. 1 to 5, the vertebral alignment/fixation assembly 10of the current invention consists of three main components: ahemispherical pedicle screw 12, a coupler unit 14 which functions as auniversal joint, and a securing nut 16.

The hemispherical pedicle screw 12, as shown in FIG. 1, comprises asubstantially hemispherical head portion 18, a neck portion 20 and ashaft portion 22. Although in FIG. 1 the shaft 22 is shown as having agenerally cylindrical body 24 and a tapered tip 26 with a thread 28dispose along the length of the shaft 22, any shaft design, thread pitchor tip taper suitable for insertion into a vertebral body can beutilized in the current invention. In the embodiment shown in FIG. 1,the tapered tip 26 of the pedicle screw shaft 22 further comprises aslotted groove 30 running longitudinally along the shaft, designed suchthat the screw is self-tapping easing the insertion of the pedicle screw12 into the vertebral body.

The head portion 18 of the pedicle screw 12 comprises a substantiallyhemispherical shape. The substantially hemispherical shape of the headportion 18 of the screw 12 is a portion or section of a sphere. Althoughin the embodiment shown, the section or portion of the sphere comprisingthe head 18 of the screw 12 is greater in extent than a hemisphere, itshould be understood that any external contour which is equidistant froma center point of the head portion 18 could be utilized. In theembodiment shown in FIG. 1, the major cross-section of the substantiallyhemispherical head portion 18 includes at least 270 degrees of a circle.

The hemispherical head portion 18 also has a recess 32 disposed therein(shown in phantom in FIG. 1). The recess 32 defines a engagement pointfor the application of torque from a torque driving tool 33 for drivingthe screw 12 into a bone. The specific shape of the recess 32 may bechosen to cooperate with any suitable screw-driving tool 33, as shown inFIGS. 4a and 4 b. For example, the recess 32 may comprise a slot for aflat-headed screwdriver, a crossed recess for a phillips headscrewdriver, a hexagonally shaped hole for receiving an allen wrench, ora “figure-8” shaped driver. In a preferred embodiment, a square-headedhole for a square screwdriver or socket-type wrench is utilized.Although the recess 32 is shown to be co-axial with the general elongateaxis of the screw shaft 22, it should be understood that any arrangementof recess 32 and screw 12 can be utilized such that sufficient torquemay be applied to the screw 12 to drive it into a bone.

The head portion 18 of the screw 12 is connected to the shaft portion 22at a neck portion 20. In relation to each other, the diameter of theshaft 22 should be less than the diameter of the semi-spherical head 18,and the neck 20 of the screw 12 should be preferably narrower than thewidest portion of the shaft 22. A pedicle screw 12 according to theinvention having such dimensional relationships is preferable becausethe screw may be locked at a variety of angles with relation to thecoupling unit 14 while still being securely joined to the couplingelement 14 (embodiments of which are shown in FIGS. 1, 2 and 5).Although any biocompatible material having suitable strength anddurability characteristics may be utilized, the pedicle screw 12 ispreferably made from surgical grade titanium or stainless steel.

One exemplary embodiment of the universal joint coupling element 14 ofthe present invention is shown in a side view in FIG. 1, criticalelements are shown in phantom. The coupling element 14 comprises agenerally cylindrical tubular body which defines an inner passage 34having an inner wall 36. The inner passage 34 comprises an uppergenerally cylindrical portion 38 and an inwardly curved lower portion40. The inwardly curved lower portion 40 defines a socket, into whichthe head 18 of the screw 12 may rotatingly engage. The bottom surface 42of the coupling element 14 includes an opening 44 defining a passage 46such that the shaft 22 of the screw 12 may extend therethrough and passoutside the body of the coupling element 14. To securely engage thescrew 12 within the coupling element 14, the dimensions of the opening44 and passage 46, must be greater than the diameter of the shaft 22 ofthe screw 12, but less than the largest diameter of the head 18.

The cylindrical upper portion 38 of the coupling element 14 includes apair of vertically oriented, channels 48 having rounded bottom surfaces50 and open top portions disposed on opposing sides of the couplingelement 14. In combination the channels 48 form engagement point for anelongated fixation rod 60. In addition the channels 48 divide the wall52 of the coupling element 14 into upwardly extending members 54 and 56.As shown in the embodiment illustrated in FIGS. 1, 2 and 5, the verticaldistance from the top 58 of the channels 48 to the curved bottom 50, issufficient to allow the rod 60 which is to be provided to slidinglyengage therein such that the rod 60 may be fully nested in the channels48. In addition, the curved bottom 50 of the channels 48 are arrangedsuch that the top of the head 18 of the screw 12, when fully nested inthe lower socket portion 40, extends above the edge of the curved bottom50 of the channels 48 such that a rod 60 positioned therein willpressingly engage the head portion 18 of the screw 12. The top 58 of theupper portion 38 of the coupling element 14, which comprises upwardlyextending members 54 and 56, have disposed thereon a threading 62. Theupper portion 38, and the threading 62 thereon, is ideally suited forthreadingly engage a securing nut 16.

FIGS. 2a, 2 b and 2 c show an additional feature of one exemplaryembodiment of the invention, which allows angular alignment of the screw12 up to at least a 90 degree angle with respect to the coupling element14. In this embodiment the lower portion 40 of the coupling unit 14further comprises a pair of lower slots 63 extending from the opening 44and passage 46 in the bottom surface 42 of the coupling unit 14. Thelower slots 63 are aligned on opposite sides of the bottom surface 42 ofthe coupling unit 14 such that in combination the slots 63 define asingle 180 degree passage dimensioned to allow the neck portion 20 ofthe screw 12 to move therein when the head portion 18 of the screw isfully engaged in the socket 40 of the coupling unit 14 and the couplingunit 14 is properly oriented with respect to the shaft 22 of the screw12. As shown, even in this extreme angular position, the coupling unit14 is designed such that a rod 60 inserted into the channels 48 willpress against the head portion 18 of the screw 12 and at the urging ofthe securing nut 16 engage and fix both the rod 60 and in turn thecoupling unit 14 into alignment.

The top securing nut 16 is shown in top view in FIG. 3a, in side view inFIG. 3b, and in cross section in FIG. 3c. The nut 16 comprises an innerthreading 64, which is intended to mate with the threading 62 on theupwardly extending members 54 and 56 of the upper portion 38 of thecoupling element 14. The nut 16 also comprises an inner plug portion 65having a bottom surface 66 which is intended to seat against the topsurface of the rod 60 seated in the coupling element 14, providing ameans for driving the rod 60 downward and against the head portion 18 ofthe screw 12. A central annular opening 68 is provided in the center ofthe nut 16 defining a passage 70 passing therethrough, the passage 70and opening 68 being designed such that the screw driver utilized todrive the screw 12 into the vertebral body can fit therein and can beutilized to tighten the nut 16 onto the coupling unit 14, as shown inFIG. 4b. Although the embodiment of the passage 70 shown in FIGS. 3a to3 c terminates in the middle of the plug 65 of the nut 16, the passage70 could also transect the plug 65 forming a conduit between the opening68 and the bottom surface 66.

In the preferred embodiment shown in FIG. 1, the bottom surface 66 ofthe nut 16 further comprises a plurality of raised metal teeth 72designed to bitingly engage and press into the rod 60 providingadditional frictional engagement between the rod 60 and the vertebralalignment assembly 10 such that the possibility of a mechanical shockjarring the rod 60 loose from the vertebral alignment assembly 10 isreduced. In another preferred embodiment, the rod 60 is manufacturedwith a rolled or corrugated finish to improve the frictional engagementbetween the rod 60 and the teeth 72 on the bottom surface 66 of the nut16.

FIGS. 4a and 4 b show the engagement of a driver 33 with the vertebralalignment assembly 10 to first engage the screw 12 into the vertebralbody 74, as shown in FIG. 4a, and then to engage the securing nut 16onto the coupling unit 14, as shown in FIG. 4b. As shown in FIG. 4a, thecoupler unit 14 is designed such that the screw driver 33 can fit insidethe inner passage 34 of the coupler 14 and engage the recess 32 of thehead portion 18 of the screw 12 to drive the screw 12 into the vertebralbody 74. As shown in FIG. 4b, the securing nut 16 is further designedsuch that the screw driver 33 can engage nut opening 68 to secure thenut 16 on the coupling unit 14 and thereby fix alignment rod 60 intocoupling unit 14 and further secure the alignment of the coupling unit14 in relation to the axis of the screw 12.

Referring now to FIG. 5, the coupling element 14 is shown with the screw12 inserted therethrough, and the head 18 of the screw 12 nested in thelower socket portion 40 of the coupling element 14. The shaft portion 22of the screw 12 is inserted downward, through the interior passage 34 ofthe coupling element 14, and out through the opening 44. In thisposition, the curved undersurface of the head portion 18 rests againstthe inwardly curved bottom surface 42 of the lower socket 745 portion40, and is prevented from translating further downward by the dimensionsof the opening 44. Meanwhile, the uppersurface of the head portion 18 ispressed against the rod 60 which is pressed into the head portion 18 bysecuring nut 16 thereby simultaneously preventing the rod 60 from movingout of the coupling unit 14 and preventing the coupling unit 14 frommoving relative to the screw 12.

FIGS. 6 and 7, show a side view of the fully locked coupling element,rod, and screw system in relation to a vertebral body 74. FIG. 6 showsthe vertebral alignment/fixation assembly 10 of the invention anchoredtraditionally in a plurality of vertebral bodies with an optionalcrosslink stabilizing bar. FIG. 7 shows the vertebral alignment/fixationassembly 10 of the invention anchored into the ileum bone with the screw12 aligned at a 90° angle with reference to the coupling unit 14. Withreference to these Figures, the preferred method of assembly andalignment of vertebral bodies is described.

First, a pre-drilled hole 76 is provided in the bone 74, into which thescrew 12 is to be anchored. The hole 76 may be pretapped, or, asdescribed above, the external threading 28 at the tip portion 24 of thescrew 12 may include a self-tapping slot 30. In either case, duringassembly, the tip 26 of the screw 12 is inserted through the interiorpassage 34 of the coupling element 14 until the shaft 22 of the screw 22extends out of the coupling element 14 and the head 18 of the screw 12is engaged in the lower socket portion 40 of the coupling unit 14. Atthis point in the assembly process, the coupling element 14 has thecapacity to rotate relative to the screw 12. A screw-driving tool 33 isthen aligned with the recess 32 in the head 18 of the screw 12 so thatit may be driven into the preformed hole 76 in the bone 74.

After the screw 12 has been driven into the hole 76, the couplingelement may be rotated relative to the screw 12, to align the couplingelement 14 such that a support rod 60 may be engaged within the rodreceiving channel 48 and properly aligned according to the surgeon'swishes. As shown best in FIG. 5, and previously discussed, the bottom ofthe rod 60 seats on the top of the head portion 18 of the screw 12, andnot fully on the bottom curved surface 50 of the channels 48.

After the rod 60 is positioned within the coupling element 14, the toplocking nut 16 is threaded onto the threading 62 of the upwardlyextending members 54 and 56. The nut 16 is then screwed down onto thecoupling element 14 until the lower surface 66 of the engaging portion65 of the nut 16 seats against the top surface of the rod 60. As the nut16 descends onto the coupling element 14, the rod 60 is driven downwardby the engaging portion 65 of the nut 16, causing the rod 60 to engagethe head 18 of the screw 12 and to push the head portion 18 of the 3screw 18 downward pressingly engaging it within the socket 40 of thecoupling element 14. This downward translation permits the bottom of therod 60 to seat against the bottom surface 50 of the channels 48, andcauses the head 18 of the screw 12 to be crush locked to the inwardlycurved surface 40 of the coupling element 14. The force also engages theteeth 72 of the nut 16 into the rod 60 providing additional frictionalengagement between the coupling element 14 and the rod 60. As such, thedownward force of the bottom surface 66 of the nut 16 against the rod60, as well as the teeth 72 and the counter-force provided by the bottomsurface 50 of the channels 48 causes the rod 60 to be locked. Thislocking prevents the rod 60 from sliding relative to the assembledvertebral alignment assembly 10, locking the rod 60 to the couplingelement 14, as well as the screw 12 to the coupling element 14.

In addition to these basic components, fixation hardware could also beprovided to fix the spine into the desired alignment. The fixationhardware may comprise clamps, which are designed to mate with the top orside of the pedicle screw, bendable fixation rods or plates, which runbetween the clamps on the various pedicle screws attached either todifferent vertebral bodies or at different points on a single vertebralbody, and bolts, also designed to mate with the clamps such that theclamps can be tightened onto and fix the fixation rods into place. Inaddition, as shown in FIG. 6 the fixation hardware may comprisecrosslinks of any design suitable for attachment to the alignmentassembly 10 of the current invention. For example, although thecrosslink shown in FIG. 6 is of fixed dimension, slotted crosslinks mayalso be used for applications in which the distance between the fixationpoints of the crosslink must be changed. In such an embodiment, theopenings in the crosslink for attaching it to the alignment assembly 10(which are shown as simple holes in FIG. 6) comprise elongated slotssuch that the crosslink may be slid relative to the alignment assembly10 along the length of the slot, thereby allowing for some degree ofadjustment in the position of the crosslink relative to the alignmentassembly.

All of the above components, including the fixation hardware can be madeof any suitable surgical material, such as, for example, stainless steelor titanium.

Although specific embodiments are disclosed herein, it is expected thatpersons skilled in the art can and will design alternative vertebralalignment/fixation screws that are within the scope of the followingclaims either literally or under the Doctrine of Equivalents.

What is claimed is:
 1. A vertebral alignment/fixation assemblycomprising: a screw comprising an elongated threaded shaft defining ascrew axis with a substantially hemispherical head having a driverengaging recess disposed therein arranged at one end of the shaft and atapered tip arranged at the other end of the shaft; a coupling elementcomprising a cylindrical body having an exterior threading disposed onan upper surface and defining an axial bore through which said screw maybe inserted, said bore having a narrowing inwardly curve lower surfacedefining a socket designed to engage the substantially hemisphericalhead of the screw such that the head of the screw is prevented frompassing therethrough and such that the screw may be rotated therein toadjust the angle between the axis of the screw and the axis of the bore,said coupling element further comprising a pair of opposing upperchannels formed in the top of said coupling element such that anelongated rod may be received therein and a pair of opposing lowerchannels formed in the bottom of said coupling element designed to allowthe shaft of the screw to move therethrough, the lower channels beingdesigned such that the angle between the axis of the screw and the axisof the coupling element can be adjusted to at least 90 degrees; and asecuring nut, mateable with said exterior threading, the nut having anengaging portion designed to fit within the bore to engage the elongatedrod, the engaging portion further comprising a plurality of engagingteeth designed to frictionally lock the rod within the upper channel ofthe coupling element.
 2. A vertebral alignment/fixation assembly asdescribed in claim 1, wherein the angles between the axis of the screwand the axis of the coupling element can be adjusted to at least 100degrees.
 3. A vertebral alignment/fixation assembly as described inclaim 1, wherein the assembly is made of stainless steel.
 4. A vertebralalignment/fixation assembly as described in claim 1, wherein the recessis designed to receive a screw driver from the group consisting of:flat-headed, phillips head, alien wrench, and square headed.
 5. Avertebral alignment/fixation assembly as described in claim 1, whereinthe nut further comprises an axial recess identical to the recessdisposed on the screw head.
 6. A vertebral alignment/fixation assemblyas described in claim 5, wherein the nut recess is designed to receive ascrew driver from the group consisting of: flat-headed, phillips head,allen wrench, and square headed.
 7. A vertebral alignment/fixationassembly as described in claim 1, wherein the screw further comprises aslotted groove disposed longitudinally along the tip and designed toallow the screw to be self-tapped.
 8. A vertebral alignment/fixationsystem comprising: at least one elongated rod; and at least onevertebral alignment/fixation assembly comprising: a screw comprising anelongated threaded shaft defining a screw axis with a substantiallyhemispherical head having a driver engaging recess disposed thereinarranged at one end of the shaft and a tapered tip arranged at the otherend of the shaft, a coupling element comprising a cylindrical bodyhaving an exterior threading disposed on an upper surface and definingan axial bore through which said screw may be inserted, said bore havinga narrowing inwardly curve lower surface defining a socket designed toengage the substantially hemispherical head of the screw such that thehead of the screw is prevented from passing therethrough and such thatthe screw may be rotated therein to adjust the angle between the axis ofthe screw and the axis of the bore, said coupling element furthercomprising a pair of opposing upper channels formed in the top of saidcoupling element such that said at least one elongated rod may bereceived therein and a pair of opposing lower channels formed in thebottom of said coupling element designed to allow the shaft of the screwto move therethrough, the lower channels being designed such that theangle between the axis of the screw and the axis of the coupling elementcan be adjusted to at least 90 degrees, and a securing nut, mateablewith said external threading, the nut having an engaging portiondesigned to fit within the bore to engage the elongated rod, theengaging portion further comprising a plurality of engaging teethdesigned to frictionally lock the rod within one of said upper channelsof the coupling element.
 9. A vertebral alignment/fixation system asdescribed in claim 8, wherein the angles between the axis of the screwand the axis of the coupling element can be adjusted to at least 100degrees.
 10. A vertebral alignment/fixation system as described in claim8, wherein the system components are made of stainless steel.
 11. Avertebral alignment/fixation system as described in claim 8, wherein therecess is designed to receive a screw driver from the group consistingof: flat-headed, phillips head, allen wrench, and square headed.
 12. Avertebral alignment/fixation system as described in claim 8, wherein thenut further comprises an axial recess identical to the recess disposedon the screw head.
 13. A vertebral alignment/fixation system asdescribed in claim 12, wherein the nut recess is designed to receive ascrew driver from the group consisting of: flat-headed, phillips head,alien wrench, and square headed.
 14. A vertebral alignment/fixationsystem as described in claim 8, wherein the screw further comprises aslotted groove disposed longitudinally along the tip and designed toallow the screw to be self-tapped.
 15. A vertebral alignment/fixationsystem as described in claim 8, further comprising at least one piece offixation hardware designed to engage the at least one vertebralalignment/fixation assembly, the fixation hardware selected from thegroup consisting of: crosslinks, clamps, plates and rods.
 16. Avertebral alignment/fixation method comprising: providing a vertebralalignment/fixation system as described in claim 8; inserting the screwinto the coupling element such that the head of the screw engages thesocket of the coupling element; driving the screw into a vertebral body;inserting a rod into the upper channels of the coupling element;angularly aligning the coupling element and rod with the vertebral body;tightening said securing nut onto the coupling element such that theengaging portion of the nut pressingly engages the rod, forcing the rodinto the head of the screw thereby fixedly attaching the rod within thecoupling element and preventing the coupling element from beingangularly rotated with respect to the screw.
 17. A vertebralalignment/fixation method comprising utilizing a vertebralalignment/fixation system as described in claim 8 to align at least onevertebral body.
 18. A vertebral alignment/fixation method comprisingutilizing a plurality of vertebral alignment/fixation assemblies asdescribed in claim 1 to align at least one vertebral body.